Determination Of Heavy Metals And Other Elements In Soil Under Different Digestion Systems By ICP-MS And ICP-OES

With economic and industrial development,soil pollution has become increasingly severe,especially soil heavy metal pollution,because of its characteristics such as concealedness,long-term,cumulative and irreversible,and the hazards that caused by it tend to be later known,so the research of heavy metal pollution analysis techniques for soil is imminent,which is in line with the national needs of the country,and the technical support of the environmental problems.And for now,Inductively Coupled Plasma Mass Spectrometry（ICP-MS）and spectral analysis（ICP-OES）have been widely used in many advantages,whereas the pollution status is not the same for different regions in China,so that it is difficult to find another unified method of ICP-MS or ICP-OES analysis for them,especially too high in organic content.The general acid solution is difficult to completely dispel,which will have a deviation of the test result.For exsamples,when using hydrogen peroxide and hydrochloric acid to digest soil samples with high organic content,organic matter is often adsorbed on the wall of the bomb,and the adsorbed organic matter will enrich some metal elements,resulting in low element detection value;when perchloric acid is used to remove organic matter,it may cause explosion due to improper use,and it is difficult to drain it because of high boiling point in the process of acid discharge,and there is also the risk of sample spatter due to its strong oxidizing reaction for hydrogen peroxide instead of perchloric acid,resulting in a low measured value.This paper explores the digestive method for soil samples with high organic matter,as little use of highly toxic,chemical reagents,which can be measured more efficiently and quickly for13 heavy metal elements such as Cr,Ni,Cu,Zn,Cd,Pb,Al,Ca,Fe,K,Mg,Mn and Na.Select8 soil standards（GSS-1a～GSS-8a）for research objects,attempting to prepare soil samples with different conditions,and then add nitric acid and hydrofluoric acid to further disintertaine,and other four conventional digestion methods(M-1:H₂O₂-HNO₃-HF;M-2:HCl-HNO₃-HF;M-3:HNO_3:3HCl-3HNO_3:HCl-HF;M-4:H₂O₂-HCl-HNO₃-HF)are compared,in order to provide an effective method for batching soil samples with organic matter,the main research results are as follows:1.The experimental results of different calcination temperatures and different calcination times show that when the temperature rise rate is set as 3℃/min and the temperature rises to550℃for 2 hours,the removal of organic matter is more thorough,and the accuracy and precision of the determination（（RSD<2%））of elements are better than those of the other two conditions.2.Five different digestion systems were used to treat the standard samples（GSS-1a～GSS-8a）,and the concentrations of Cr,Ni,Cu,Zn,Cd and Pb in the samples were determined by ICP-MS.The results of five digestion methods showed that the measured values of M-5 were consistent with the standard values within the error range,the recovery rate of each element is95%～110%,and the stability and precision of the determination results were better than those of the other four digestion methods.When peat sample with burning loss of more than 20%was applied,the results obtained by the ash digestion system were more accurate and accurate than those obtained by other digestion systems.3.Using ICP-OES determination of the five different causing the digestion way of the standard samples（GSS-1a～GSS-8a）of Al,Ca,Fe,Mg,Mn,Na,K and other elements,the results showed that the dry ashing method may lead to the samples of main elements in the determination of K,Ca,Na and Mn element results were low,further application in soil of the actual sample digestion experiment also found that the higher the amount on ignition（LOI）,ashing system of K,Ca,Na,Mn and other elements of test values would be significantly lower,especially K element is most obvious.The analysis may be caused by the loss in the process of ashing,which requires further optimization of the conditions for experimental verification.Comprehensive the above results,the use of dry ashing（heating rate 3℃/min,up to550℃,the duration of 2 hours）-nitric acid-hydrofluoric acid digestion system to deal with different area standard material soil samples,and then using ICP-MS determination of Cr,Ni,Cu,Zn,Cd and Pb of the concentration.It was found that the error range was consistent with the standard value,and similar results were obtained after digestion of 15 actual soil samples with different organic matter contents.However,the dry ash method in the digestion system may lead to partial loss of K,Ca,Na,Mn and other major elements in the soil samples.Therefore,the preliminary results revealed that this method was suitable for ICP-MS determination and analysis of heavy metal elements in soil samples with high organic matter content,with less acid addition,less interference and relatively simple operation.